Year	Percent
1968	52.12
1969	75.84
1970	59.94
1971	18.4
1972	13.13
1973	15.9
1974	10.1
1975	7.948
1976	22.18
1977	20.4
1978	11.94
1979	17.29
1980	29.92
1981	17.91
1982	19.78
1983	19.02
1984	23.14
1985	21.94
1986	22.02
1987	24.6
1988	29.97
1989	27.91
1990	14.28
1991	5.593
1992	8.951
1993	9.942
1994	14.99
1995	19.61
1996	16.05
1997	11.52
1998	13.23
1999	9.896
2000	12.79
2001	13.12
2002	17.36
2003	17.36
2004	19.96
2005	13.44
2006	14.93
2007	20.11